Continued goals for this ongoing Outstanding Investigator Grant (OIG) are to develop and use biostatistical, biomathematical and epidemiologic methods aimed at reducing cancer occurrence. The research objectives are twofold: first, to develop new methods for the conduct of epidemiologic studies of cancer etiology in relation to modifiable personal characteristics, and second, to use these methods to collect and analyze data relating such characteristics to site- specific cancer occurrence. Both the statistical and epidemiologic work during the past four years has focussed on cancers of the colorectum, ovary, breast and prostate. The most important research accomplishments have been a study of colorectal cancer in Chinese in the US, Canada and China in relation to diet, physical activity and body size, a collaborative analysis of raw data from 12 US case- control studies of ovarian cancer, and three studies of prostate cancer. This work has been featured in editorials in several scientific journals. Future plans are to address statistical problems and epidemiologic issues that have emerged in the study of cancers of the prostate and ovary. Both the methodological and the epidemiologic effort will focus on improved understanding of the combined effects of hereditary predisposition and modifiable lifestyle characteristics in the etiologies of these cancers.